It will be the second trip to the region for Bush who has ramped up relief operations in recent days after acknowledging that the initial effort had been unacceptable.

On Sunday, the president taped a televised appeal for donations on behalf of the American Red Cross, urging his compatriots to give "more blood, money and time" to help victims of the hurricane.

"I just passed the place where volunteers and staffers are taking calls from around the country, and the response has been good, but there's more that needs to be done," Bush said.

A week after Katrina slammed into the US Gulf coast and triggered the worst natural calamity in US history, most survivors in the worst-hit city of New Orleans had been evacuated, leaving the once vibrant jazz capital a floating mortuary of decomposing corpses.

Medical officials on Sunday said 59 bodies had been recovered so far, but stressed that number was only a fraction of the real death toll which local, state and federal officials estimated in the thousands.

One major unknown is how many bodies may be trapped in homes where people opted to ride out the storm, only to drown when the floodwaters came pouring in.

"We've seen more people dead than alive," said Michael Lester, a volunteer helping rescue teams conduct a house-to-house search by air and boat for any remaining survivors.

Among those who were found, not all were overjoyed at the prospect of finally being evacuated.

One man brought to dry land insisted he wanted to return to his home, despite pleas by paramedics who said he would soon run out of food and drinking water.

"Everything flooded out of the house but I still have a bed on the second floor; I'm staying," said Carl Roberts, 74.

But Homeland Security chief Michael Chertoff made it clear that evacuation was not a matter of choice.

"We are not going to be able to have people sitting in houses in the city of New Orleans for weeks and months while we de-water and clean this city with the hope that we're going to continue to supply them with food and water," Chertoff said.

Secretary of State Condoleezza Rice and Defense Secretary Donald Rumsfeld visited stricken areas on Sunday as the administration sought to counter accusations that it dragged its feet in responding to the disaster.

Rumsfeld emphasised the unprecedented scale of the destruction, while Rice rejected suggestions that the predominance of poor, black people among the survivors had fuelled official indifference.

"I don't believe for one minute that anybody allowed people to suffer because they were African-Americans. I just don't believe it," Rice said.

Bush first visited the region on Friday, after which he signed a special 10.5 billion dollar aid package for hurricane victims and ordered more than 7,000 elite troops to reinforce the National Guard deployed in the Gulf coast.

Despite the extra numbers, security remained a concern in New Orleans which had experienced five days of shocking lawlessness in Katrina's wake.

On Sunday, a running gunbattle erupted as contractors for the US Army Corps of Engineers were shot at by unidentified gunmen and Louisiana state police returned fire.

Amid all the misery, there were some glimmers of hope and optimism as power was restored to some areas of New Orleans and a handful of survivors staged an impromptu gay parade in the city's famed French Quarter.

"We're trying to bring up everyone's morale," said student Candice Jamieson, 21.

The reality however was still extremely bleak and officials made it clear that the entire country should prepare for the worst as the recovery of the bodies got underway.

"It is going to be about as ugly a scene as we've witnessed in this country," Chertoff said. "I really want to tell people that we have got some tough days ahead of us."

New Orleans Mayor Ray Nagin revealed that several city police officers and firefighters had been so traumatised by the events of the past week that they had committed suicide.

For those who finally made it out of the city, evacuation was not the end of their ordeal, with packed buses reportedly turned away from shelters outside the disaster area.

Texas Governor Rick Perry warned that his state, which has taken in nearly a quarter of a million refugees, was nearing the limit of its resources as he organised airlifts in Houston and Dallas to take evacuees to other states.

At New Orleans airport, which was transformed into a holding pen for the elderly and infirm as well as a gateway for the departing, dozens of people from nursing homes and hospitals lay dying on stretchers on the floor.

"Their organs are shutting down. They are septic. They are storm victims," said chaplain Mark Reeves, 43, from the federal Disaster Medical Assistance Team.

The spectre of disease also haunted recovery efforts with doctors fearing the fetid waters and squalid conditions in shelters could breed cholera or typhoid, or spawn mosquitoes carrying malaria or West Nile Virus.

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